The carbide evolution behavior of a high tungsten nickel-based superalloy during long-term aging at 1 000 ℃ was investigated by several analysis methods such as SEM

TEM and EPMA. The results indicate that primary MC carbides of the alloy are decomposed into M

6

C carbides

of which the amount is increased as the prolongation of thermal exposure time. When exposed for 500 h

the morphology of M

6

C carbides is converted from granular to blocky

and gradually transformed into rod-like after thermal exposure for 1 000 h. The morphology of M

6

C carbides of the alloy is dominated by the needle-like after thermal exposure for 1 500 h.